As conventional shock absorbing apparatuses, the following have been known heretofore: hydraulic buffering apparatuses in which pistons compress liquids, thereby relieving shocks; or those which absorb shock energies by pneumatic compression resistance while letting air escape through air pin holes; and the like.
Moreover, in recent years, many shock absorbing apparatuses have been used extensively, shock absorbing apparatuses which are made by disposing a large number of resinous ribs inside door trims, and which absorb shock energies by means of the buckling of the resinous ribs and the occurrence of cracks therein. As for these resinous ribs, the following have been general ones: those which comprise a bottomed cylindrical outer-wall portion and checkered ribs that are formed in the internal space of the outer-wall portion, and that divide the internal space into a plurality of minor compartments.
However, in the method where shocks are absorbed using the hydraulic buffering apparatuses, spring back acts thereon because there is no way out for the liquids to escape, and thereby it is difficult to absorb shock energies efficiently. Moreover, height dimensions are needed in directions in which impactive forces are applied.
Moreover, even in the case of using a hollow bellows-shaped shock absorber possessing an air pin hole and absorbing shock energies by pneumatic compression resistance while letting air escape through the air pin hole, height dimensions are also needed in directions in which impacts are applied, and thereby this method has not been applied to narrow parts and parts where any height dimensions are not adoptable.
Moreover, in those which shock energies are absorbed by means of the buckling of the resinous ribs and the occurrence of cracks therein, although buckled states occur stably by means of setting up the configuration and material quality of the resinous ribs suitably, the occurrence circumstances of cracks becomes unstable depending on the material quality and molding conditions, and the like. Accordingly, while being accompanied by the variations of the resinous ribs and so forth, it should be inevitable to vary the configuration of the resinous ribs for each of the variations, and consequently there is such a drawback that the costs and man-hour requirements for manufacturing the molds become enormous.
Hence, in Japanese Unexamined Patent Publication (KOKAI) No. 9-254,727, a shock absorbing apparatus is proposed therein, the shock absorbing apparatus comprising: a main body, which possesses a hollow section that is surrounded by a plate-shaped outer wall portion; an inclusion, which is filled in the hollow section and in which a liquid makes the major component; and a through hole, which is disposed in the main body so as to communicate the hollow section with the outside and through which the inclusion is discharged to the outside gradually by means of a force of shock that is applied to the main body; and the shock absorbing being constituted so as to absorb the shock by means of resistance that arises when the inclusion passes through the through hole.
In accordance with this shock absorbing apparatus, with respect to smaller shocks, the inclusion moves within the hollow section as being accompanied by the deformation of the main body, and accordingly buffering effect is produced by means of this setting. On the other hand, when larger shock energies are applied to the main body, the volume of the hollow section is reduced by means of the deformation of the main body, and consequently the inclusion is pushed out through the through hole by means of stresses that are accompanied therewith. And, frictional resistance acts on the inclusion when it passes through the through hole; accordingly the volume of the hollow section is reduced gradually as being accompanied by the inclusion that is pushed out gradually; and consequently it is possible to absorb shock energy efficiently by means of this setting.
Furthermore, in Japanese Unexamined Patent Publication (KOKAI) No. 11-139,341, a shock absorbing apparatus is set forth therein, shock absorbing apparatus which is equipped with a first absorbing portion for absorbing shock energy by means of buckling ribs, and a second absorbing portion for absorbing shock energy by means of circulation resistance upon discharging an inclusion to the outside.
Moreover, in Japanese Unexamined Patent Publication (KOKAI) No. 2000-272,447, a shock absorbing apparatus is set forth therein, shock absorbing apparatus which comprises a housing portion that is capable of deforming plastically and a fluid that is accommodated within the housing portion, and which absorbs shock energy by means of resistance resulting from the fluid being discharged through a minor-diameter hole, which is disposed in the housing portion, by means of housing inner-pressure rise when shock acts thereon.    Patent Literature No. 1: Japanese Unexamined Patent Publication (KOKAI) No. 9-254,727;    Patent Literature No. 2: Japanese Unexamined Patent Publication (KOKAI) No. 11-139,341; and    Patent Literature No. 3: Japanese Unexamined Patent Publication (KOKAI) No. 2000-272,447
Incidentally, in the case of a shock absorbing apparatus that absorbs shock by means of the buckling of ribs, when it collides with a colliding object, such as the head of a human body or the like that has curved surfaces, for instance, the colliding object, and the shock absorbing apparatus make a point contact at first, and thereby one of the ribs buckles; and thereafter the contact area augments gradually because the colliding object compresses the shock absorbing apparatus, and thereby a plurality of the ribs buckle. Meanwhile, as a result of the action that shock energy is absorbed by means of the buckling of the ribs, the energy that the colliding object possesses decreases gradually.
That is, the contact area comes to augment contrary to the gradually decreasing energy that the colliding object possesses, and thereby a force that is applied to a unit area of the shock absorbing apparatus decreases acceleratedly. Accordingly, at a later stage in absorbing the shock, it becomes difficult to buckle the ribs, and so there has been such a problem that the “bottom sticking” phenomenon occurs as a consequence so that the reactive force from the shock absorbing apparatus augments.
Moreover, there might also be such another problem that, at a later stage in absorbing the shock, the debris of the ribs intervene between the pressure-receiving plate portion, which has received the shock, and the facing plate portion, which faces the pressure-receiving plate portion, because the debris of the buckled ribs come to remain in the hollow section; accordingly, load rises sharply at the time when the pressure-receiving plate portion and facing plate portion come in contact with the debris of the ribs, and consequently results in the problem that the “bottom sticking” phenomenon occurs so that the reactive force from the shock absorbing apparatus augments.
On the other hand, in shock absorbing apparatuses, an energy amount that is absorbed while they undergo compression deformation is important; this energy amount can be expressed with an area under a load-stroke curve. That is, the longer a shock-absorbing stroke, a distance that enables them to be deformed by compression, is, the greater an absorbing shock amount becomes. However, in the conventional shock absorbing apparatus, the shock-absorbing stroke should be set up larger while making an allowance for the height in the aforementioned debris of the ribs, and so it has been needed to design the stroke greater by a certain extent of the height in the debris of the ribs. Accordingly, it becomes a large-size shock absorbing apparatus, and consequently there might have been such still another problem that a greater disposition space becomes necessary.